Wikipedia:Reference desk/Archives/Science/2010 June 15

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June 15

Help resolve date discrepancy of an event by finding contemporaneous citation(s)

Regarding the article Rüppell's Vulture -

This bird is considered to be the world's highest flying based on examination of feathers found in a jet engine that collided with a bird over Abidjan, Cote d'Ivoire at an altitude of 11,000m on November 29, 1973 -OR- the same date in 1975.

The source cited in article (Flight Migration by Alerstam) states 1973, however a web search finds other reliable sources quote that the event happened in 1975, an example being [[1]]. A google search doesn't particularly favor one year over the other - both dates show up frequently in a search.

To resolve the discrepancy I have tried to find an article published in 1973, 1974, 1975 or 1976 that references this event so I can establish the correct year.

I have searched the online archives at flightglobal.com and newyorktimes.com looking for any articles published from 1973 to 1976 that include the word "vulture" or "cote d'ivoire" and did not find any articles that reference the event.

I have not been able to turn up any references to the particulars of the aircraft involved (military? civilian? private? commercial? airline? flight number?...) but have assumed that the following is probably accurate:

• The aircraft was jet powered
• Event happened on November 29th
• Event happened in 1973 -or- 1975
• Event happened over Abidjan, Cote d'Ivoire
• Event happened at or around 11,000m (36,100 ft) or 37,000 ft altitude

I do not have easy access to printed archives of potentially relevant scientific journals, nor do I even know which journals would be relevant. I am not associated with a university/company that might give me "free" access to online versions of scientific journals via an organizational subscription.

If you can turn up a relevant, authoritative citation that is contemporaneous to the event, please either cite it here so I can update the article or edit the article adding the exact date and citation. Obviously if we find something published in 73 or 74 the 1975 date can't be correct, plus I'm hoping that any article contemporaneous to the event will simply state the date it happened, resolving the discrepancy without question.

I'm also willing to do more work myself, but I need the ornithology and/or aviation and/or reference experts to give me some ideas on where to look next.

Thanks. Ch Th Jo (talk) 00:48, 15 June 2010 (UTC)

(I edited this to provide more information.)

Usually Google Scholar gives better results for things like this than Google Web. I was able pretty quickly to find that the original source everybody cites is Collision between a vulture and an aircraft at an altitude of 37,000 feet, R. C. Laybourne, The Wilson Bulletin, Wilson Ornithological Society, 1974. Looie496 (talk) 03:20, 15 June 2010 (UTC)

Thanks, that's perfect. Before now I wasn't aware of Google Scholar, so thanks for that as well. Ch Th Jo (talk) 18:25, 15 June 2010 (UTC)

laxatives

Hi All. First, let me be clear that this is in no way a medical question! I was reading a trivia book and there was a story about an inmate wo used large amounts of laxatives to get skinny enough to squeeze (barey) through the bars and escape (he was caught later). My question is: what are the health risks of using large dosages of laxatives in order to "slim down?" 99.250.117.26 (talk) 01:42, 15 June 2010 (UTC)

This certianly sounds like a medical question... See the article Laxatives#Problems_with_use. The more pressing question is that how the inmate obtained large amouts of laxatives needed, and how he got through the bars which go both up and down and left to right ;) 01:47, 15 June 2010 (UTC) —Preceding unsigned comment added by 76.229.161.119 (talk)

side effects would be extreme dehydration, electrolyte imbalance, cramping... Fragrantforever —Preceding unsigned comment added by Fragrantforever (talk • contribs) 05:42, 15 June 2010 (UTC)

At the risk of stating the bleedin' obvious, we have a diarrhea article. Vimescarrot (talk) 06:02, 15 June 2010 (UTC)

Anorexia and Bulimia might have some info you'd find relevant. 63.17.59.215 (talk) 11:29, 15 June 2010 (UTC)

I'd be surprised that they'd put the bars far enough apart to allow your head to get through - and no amount of laxatives are going to shrink the size of your skull. The problem with trivia books is that they have a lot of incentive to include amazing "facts" and almost zero incentive to check that they are actually true - they are the biggest purveyors of untruth outside of the Internet! If it actually happened that way - there ought to be more sources backing it up. SteveBaker (talk) 11:53, 15 June 2010 (UTC)

Oddly enough this is reported by what might be classed as reliable sources; Google for /robert cole laxative/ for example and you'll see mentions in The Guardian and New Statesman. Of course, maybe these are just passing on trivia, but this appears to be a reliable secondary source. Tonywalton ^Talk 12:09, 15 June 2010 (UTC)

Digital Camera

If one wants to buy a digital camera, how much mega-pixel is ideal ? —Preceding unsigned comment added by Jon Ascton (talk • contribs)

If you just want to view images on your computer, 2 or 3 megapixels is fine. If you want to generate large images for printing or reproduction in magazines, then you need as high as possible. ~Amatulić (talk) 04:55, 15 June 2010 (UTC)

The chances are that any camera currently on the market will have more pixels than you need. See The Megapixel Myth (compare megahertz myth). There are a lot of other features that differentiate point-and-shoot cameras. For example, some do better in low-light conditions than others; some have better flash illumination; some have optical viewfinders while others don't; some let you control the exposure time and aperture, while others don't; some can take wider angle photos than others; some have tiltable LCD screens; some have better lenses, and some just plain take better looking pictures. Sites like dpreview.com can help you compare picture quality and features of different models. -- BenRG (talk) 05:17, 15 June 2010 (UTC)

Agree with the others, megapixels are largely irrelevant over 8-10MP unless you're wanting to make large scale prints of your photographs (I'm talking exhibition-size prints). Most cameras on the market offer this amount of megapixels because it sounds impressive even if you just want to do some photos at a friend's wedding. There are many other factors that are more important, especially with single lens reflex (SLR) cameras, most importantly of which are the speed of the lenses/apertures, ISO, noise reduction etc. Regards, --—Cyclonenim | Chat  10:01, 15 June 2010 (UTC)

I'll second the above, except I'll suggest that the "largely irrelevant" threshold is even lower. 5-6 MP, on a camera with a good lens, is more than sufficient for general use. I've blown up pictures from my 6 MP camera to 30"x20" with excellent results. If you're not going to print stuff larger than 8"x10", you can go even lower -- 3-4 MP would be fine. And as Cyclonenim noted, at this point, every new camera with a decent lens will be at this point or higher. You might want to check various consumer magazines; I'd expect that Consumer Reports (among others) has done several digital camera evaluations. — Lomn 13:10, 15 June 2010 (UTC)

You want to leave some room for people to crop and use the so called "Digital zoom". APL (talk) 14:21, 15 June 2010 (UTC)

However, CCD chips come in limited sizes. Within a given class of cameras, more pixels usually means smaller pixels, which means more thermal noise. So you may get a higher nominal resolution, but more details will be lost in the noise, and the image will look washed-out. 5 megapixels used to be the sweet spot when I looked a while back. --Stephan Schulz (talk) 14:58, 15 June 2010 (UTC)

Nobody has mentioned battery life! This is one of the the most differentiating parameters left between otherwise "equivalent" performance cameras. If this factor is important, consider the negative impact of a larger sensor, LCD screen, and more powerful processor that often go along with "high-end" cameras. This is a parameter which can vary widely between different vendors. Nimur (talk) 14:58, 15 June 2010 (UTC)

Nanostructure induced flavorings

Reading the taste and taste bud articles didn't really help answer something I've been wondering about for a long time:

Is it possible for a surface to have a microstructure (nanostructure?) at the molecular level that interacts with and stimulates taste receptors? Chemically, I guess it would be like a catalyst, that doesn't actually react with anything but instead aids in a reaction.

Such a surface would have a permanent flavor, wouldn't it? Is it feasible? ~Amatulić (talk) 04:55, 15 June 2010 (UTC)

Not really. As our article on taste buds points out, taste is generated by flavour components which are dissolved in saliva, so your nanostructured surface wouldn't get to the receptors it needs to, even if it were capable of stimulating those receptors (which isn't certain itself). In addition, much of our experience of flavour comes not from the taste buds but from smell receptors in the back of the nose – flavour is a combination of taste and smell, which is why food tastes bland when you have a cold. Obviously your surface would be volatile, and so could stimulate the smell receptors. Physchim62 (talk) 10:01, 15 June 2010 (UTC)

Moreover, taste receptors are not really on the tongue surface as much as they are on the surfaces of the taste buds, and that would even more specifically be on the lateral walls of the very small projections you may be able to see on your tongue. It would be pretty difficult to get a surface to match up with these receptors to produce the taste you'd be looking for. And Physchim62's mention of olfactory involvement is right on -- so little of "taste" is actually taste. But assuming you'd be going for a purely sweet taste (incorporating no odor, let's say), You'd have to get your nanostructure to act as ligands to the taste receptors. That's like asking for an inert nanosurface to be able to excite a muscle by reacting with the acetylcholine receptors of the neuromuscular junction -- highly unlikely. You's be able to do it with a liquid medium, and I actually do this every morning. I call it Snapple :) DRosenbach ^{(Talk | Contribs)} 12:27, 15 June 2010 (UTC)

OK, thanks. I'm not convinced of two things: (1) that the components need to be dissolved in saliva, as I can taste things that don't seem to be soluble (certain oils, nonpolar solvents, etc.) - I guess it's sufficient to be liquid; (2) that a sense of smell is needed, unless I have olfactory receptors in my mouth (my nose really doesn't work for smelling). As DRosenbach pointed out, some sweet substances have no odor.

I think what I'm really curious about is whether there are any solid substances that would have a permanent flavor without actually dissolving. Nanostructure was one possibility I thought of, but there may be a way to stimulate taste receptors chemically without actually modifying the phase of the stimulant. ~Amatulić (talk) 21:29, 15 June 2010 (UTC)

Blackberry Vs I Phone

We are big fans of the I Phone and we have been using the I Phone since its launch with very satisfying results. Initially we had the 2G 16 gb version which still works like a dream and we also have a 3G and the latest 3GS model. The I Phone 4 hasnt launched here and Im sure it would be part of our family soon.

My husband and I were talking to a friend yesterday over coffee and he was raving about his Blackberry and he said the blackberry can do several things the I Phone cant even imagine:)))

I didnt retort but I thought let me ask this question to my friends here on Wikiepedia who have a scientific bend of mind.

This question is not about personal likes and dislikes. I want to scientifically compare these two phones. When I googled it, the search results only speak about the virtues of one or the other. I would like a feature by feature comparison or a point by point comparison.

My Question is : I Phone Vs the Blackberry - what are your thoughts, ease of operation, aesthetic looks, functions, pricing - what are the plus points and negetives of these phones.

Pls feel free to give your feedback. Fragrantforever 05:39, 15 June 2010 (UTC) —Preceding unsigned comment added by Fragrantforever (talk • contribs)

For a 'scientific' comparison of the phones, the best thing to do would be to try to find the manual or description of features on the appropriate manufacturers' websites. As for opinions on aesthetic looks, pricing etc, these things are probably better sought on an internet forum (either a couple of neutral ones, or one that seems pro-iPhone and one that seems pro-Blackberry to play them off against each other) rather than a reference desk. Bear in mind that the iPhone 4 was announced only a few days ago so a lot of old comparison articles are out of date. Brammers (talk/c) 08:18, 15 June 2010 (UTC)

In Japan it's apparently very common for people to pick a phone based on features - they compare a checklist and whichever one has more wins - even if they never use those features. It results in phones packed with everything, and yet totally unusable. See this article about it. So it's impossible to compare a phone that way. Compare a phone based on what YOU will use it for. Now obviously there could be features that you would like but are not aware are possible. But just straight comparing features will give you information - but not useful information. Ariel. (talk) 09:04, 15 June 2010 (UTC)

Broadly it depends what you're wanting to do with it, I've not seen any scientific comparisons, but a number in sites like Lifehacker and Really Mobile do user comparisons. As the iPhone is increasingly being seen as an enterprise business phone it's being competed against the Blackberry but the majority of comparisons that I've seen don't include Blackberry as it's a very different device.

It's worth looking at the heritage, the Blackberry grew from a need to have a handheld email device and it's developed from that basis. The iPhone is designed first and foremost as a handheld computer.

I would suggest that you need to do your own comparison from the available information, run Blackberry, iPhone, Android and WebOS against one another.

Of course Ease of Use and aesthetics are both qualitative not quantitative so not particularly scientific measures.

By way of providing a baseline my company has recently made a decision about a new phone deployment for all of our consultants. We compared Blackberry, WebOS, Android and iPhone, opting for the iPhone as the most appropriate for our needs given the cost options that were on the table from our supplier. Blackberry is quite an old fashioned device in comparison to the other three.

ALR (talk) 10:38, 16 June 2010 (UTC)

My wife has an iPhone. She loves it, but doesn't like the fact that she can't use YouTube or most other video sites because they use Flash video, which Steve Jobs is allergic to. According to our article, the Blackberry has had Flash capability since Nov, 2009, so that would seem to be a huge plus for anyone who likes watching streaming videos. Matt Deres (talk) 16:18, 16 June 2010 (UTC)

The YouTube player is part of the standard package.

ALR (talk) 21:38, 16 June 2010 (UTC)

meringue food technology

Unsatisfied with meringue bases bought from a local store (and the squirty cream can) and wishing to emulate the excellent meringue from a village store further down the road (even the big stores don't seem to make them) I stirred two egg whites, a bit of sodium bicarbonate,cornflour and masses of castor and granulated sugar until it became semi-solid, and then put it in my fan oven for two and a half hours at 100 C. The result was like a bland lump of concrete, and I don't know where the sweet flavour of all that sugar went. Do the good meringues use microwave cooking, or is there some other secret? —Preceding unsigned comment added by 80.1.88.16 (talk) 08:52, 15 June 2010 (UTC)

Castor as in Castor oil? Why would you put that in? Also, I wouldn't put in any sodium bicarbonate, add a little cream of tartar and give it some extra whipping time for fluffiness. But in general I would start with a known working recipe, then experiment from there. Ariel. (talk) 08:59, 15 June 2010 (UTC)

The OP undoubtably means castor sugar (also spelled caster), a very fine-grained suger used in cooking, and mentioned somewhere in the Sucrose article. 87.81.230.195 (talk) 09:13, 15 June 2010 (UTC)

There are three different types of meringue, according to this site: BBC Food: Meringues. You need to ascertain from the village store which type of meringue they make and follow the correct recipe. Cooking desserts is much more chemistry than cooking savoury food is, and if you don't follow meringue recipes then you will inevitably fail. I think the problem you had originally had was to do with failing to whisk the egg whites before adding anything else, but really you need to follow the recipe. --TammyMoet (talk) 09:35, 15 June 2010 (UTC)

Shirley Corriher list four types in Cookwise: soft, hard, Swiss, and Italian. Soft meringue, as used in lemon meringue pie, use about 2 tablespoons sugar per egg white, with sugar added gradually. Hard meringues, as used in hard meringue candies, use about ¼ cup sugar per egg white. Swiss meringue is very stiff and used for decorations/icing, and is made by beating sugar and eggs over boiling water. Italian meringue is used in puddings, and is made by drizzling a "hard-ball stage" (248F/120C) sugar syrup into well beaten egg whites. Corriher adds cornstarch to soft meringues, but omits it for hard meringues (indicating that the cornstarch keeps them from being "light"). I've never heard anyone advocate adding basic ingredients (like sodium bicarbonate), it's always slightly acidic, like cream of tartar or using a copper bowl. The acid stabilizes the foam. By adding base you may have overbeaten the whites before they set, causing them to be tough. For soft meringue, you want to beat just until the "soft peak" stage (where peaks form when you pull the beaters out of the foam, but where the the tops curl over under their own weight). For hard meringues, you beat a little further, until the "hard peak" stage (glossy peaks form, but don't curl over). Note that you don't need bicarb for leavening - the bubbles in meringue come from the whipping process, not from carbon dioxide generation. -- 174.24.195.56 (talk) 14:56, 15 June 2010 (UTC)

Make that five types - four from Shirley Corriher and the industrial meringue from the OP. Richard Avery (talk) 17:55, 15 June 2010 (UTC)

Instability of Manganese(III) fluoride

Why is manganese(III) fluoride so unstable? Manganese(III) oxide is much more stable, even though oxide is more easily oxidized than fluoride. --Chemicalinterest (talk) 11:40, 15 June 2010 (UTC)

It's not unstable (the article was misleading when it said that it will release F₂ on heating). It may well hydrolyse in moist air, but then so will most metal fluorides – that's why you must store them in polythene bottles instead of glass bottles – and hydrolysis is not what we usually mean by "unstable".

2MnF₃ + 3H₂O → Mn₂O₃ + 6HF

So, to anticipate your next question: "why do they hydrolyse?" Because the oxides are even more stable, and hydrogen fluoride is a pretty low energy molecule as well. And why are the oxides even more stable? Well the quick answer is because their lattice energy is higher. If you take the approximation of a pure ionic bond (not a very good approximation for the transition metals, but for the sake of illustration), then Coulomb's Law says that the strength of the bond is proportional to the product of the two opposing charges: so an Mn³⁺–O²⁻ ionic bond is (roughly) twice as strong as an Mn³⁺–F⁻ ionic bond. There are several other factors that come into it as well, but I'll leave you with this for starters! Physchim62 (talk) 12:03, 15 June 2010 (UTC)

Fluorides normally react with glass to form hexafluorosilicates. I thought that it spontaneously released F₂ gas, which is what I had a hard time believing. --Chemicalinterest (talk) 12:23, 15 June 2010 (UTC)

The release of F₂ is incorrect, at least at normal temperatures (all halides will decompose if you heat them strongly enough, but we're talking about thousands of degrees for most of them). As for fluorides reacting with glass to form hexafluorosilicates, the reaction is very slow in the absence of moisture: but, as you usually have a bit of moisture around when you're using these things, it is much better to store them in polythene bottles than to have a glass bottle shatter as you pick it up off the shelf! Physchim62 (talk) 12:30, 15 June 2010 (UTC)

Can you check the temp? [2] says decomposes at 600C - there's a difference between decomposes liberating F2, and melts (or boils) whilst retaining the same stoichiometry - I think the original statement may be roughly correct.87.102.18.94 (talk) 13:04, 15 June 2010 (UTC)

Also many flourides do not decompose at temperatures below that which will produce atomic fluroine - eg MnF2 - I think the difference is between 'eventually decomposes to elements' and 'decomposes with formation of a more stable flouride'87.102.18.94 (talk) 13:06, 15 June 2010 (UTC)

(it is unstable - but we need the Temp.) See also [3] and http://www.1911encyclopedia.org/Manganese - "manganic flouride".87.102.18.94 (talk) 13:11, 15 June 2010 (UTC)

Fair enough. I was going on Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. p. 1224. ISBN 978-0-08-022057-4., which says it is "thermally stable". Physchim62 (talk) 13:39, 15 June 2010 (UTC)

It's good to at least 300C :) —Preceding unsigned comment added by 87.102.18.94 (talk) 19:30, 15 June 2010 (UTC)

They might be talking about the hydrate, (one link was) though I still think decomposition to CoF2 is likely.87.102.18.94 (talk) 17:31, 15 June 2010 (UTC)

Decomposition to MnF₂ is more plausible! ;-) Physchim62 (talk) 19:33, 15 June 2010 (UTC)

Bats, birds and convergent evolution

I remember reading once about theory of convergent evolution, and as an example, the text offered that it was much more parsimonious to speculate that insects, birds and bats (which are very different organisms) each evolved flight independently than to suggest that they had a much more recent common ancestor that evolved flight once and then split into these three lineages afterward. So I was wondering just how different bats and birds are and I came up with the following list. If anyone can add constructively to my pondering, that'd be great.

1. Bats are mammals in every sense of the word and birds are not. Perhaps this is the most glaring imparsimoneousness of the suggestion that a recent common ancestor of bats and birds produced bats that then converged perfectly with a previously existing mammal line.
2. Another likely glaring imparsimoneousness of the aforementioned speculation relates to the evolutionary timeline, with which I am altogether unfamiliar. I sort of got stuck at the Reptiliomorpha article because it seems that there's lots of bird/reptile talk but not a lot of bird mammal talk about convergence/divergence.
3. For me, it seems very difficult to discuss any physiologic/anatomic differences because I don't know how to give the proper weight to the evolutionary significance of any particular convergence/divergence, as I'm merely a freelance zoologist and not an evolutionary biologist. Mammals converged with birds with Protheria in terms of cloaca and egg-laying, so who's to say that any of the various traits we all know that separate birds from bats (beaks, etc.) count for that many parsimony points in the tally I'm trying to make?

DRosenbach ^{(Talk | Contribs)} 12:19, 15 June 2010 (UTC)

The "traditional" argument (from the days before routine DNA sequencing) comes from the structure of the skull, in particular the temporal fenestrae (openings in the side of the skull). All birds (and most modern reptiles) are diapsid, that is they have two temporal fenestrae on either side of the skull; all mammals (including bats and Protheria) are synapsid, that is they have a single temporal fenestra on each side of the skull. The appearance of temporal fenestrae dates to a bit more than 300 million years ago, long before there were any creatures that could be described as mammals or birds, and has been preserved through later fossils, so it's thought that the temporal fenestrae are a marker for evolutionary divergence. Physchim62 (talk) 12:56, 15 June 2010 (UTC)

Very helpful -- thanx! DRosenbach ^{(Talk | Contribs)} 15:41, 15 June 2010 (UTC)

If I personally were writing a textbook, I would not frame this issue in terms of parsimony -- parsimony is a useful criterion mainly when the evidence is relatively sparse. In this case we know enough to actually tell the story of how things happened -- we know for example that protostomes and deuterostomes (the superphyla containing insects and vertebrates respectively) diverged over 500 million years ago, when complex life existed only in the sea, and that synapsids and diapsids diverged over 300 million years ago, when no vertebrate could fly and even walking was pretty crude. Looie496 (talk) 16:10, 15 June 2010 (UTC)

Looie -- I think you're making my point without even realizing it. The reason why we can state "we know what happened" even though no one was there is because it makes sooooooo much sense to state proposition A and so little sense to state proposition B. Proposition A would be that synapsids and diapsids split and then much much much later, each developed their own flying organisms, while proposition B would be that the split occurred between flying and nonflying and that convergent evolution brought some initial divergents back to what appears to have been a continuous line of protostome heritage. Granted it sounds a bit odd to anyone who has even a somewhat realistic perspective of evolutionary biology, but I'd say that I meet less than 1 new person a day who would have such a grasp. On the contrary, I find that once explained, the parsimony argument will essentially state the same thing but be more palatable to the untrained mind. Thanks for your additions to the response -- it served to concretize my understanding of this matter. DRosenbach ^{(Talk | Contribs)} 20:45, 15 June 2010 (UTC)

The problem with any theory of extreme convergent evolution in which so very many attributes of mammals, birds and insects would have had to be converged - is that the flight mechanisms of birds, bats and mammals are dramatically different. If they came from common ancestors, why don't insects and bats have feathers? Why do birds use modified fore-arms to form the structure of their wings - where bats are using modified fingers and insects are using yet some other modified structure (the 'notum'). Their flight mechanisms are so spectacularly different, it's really inconceivable that these flight mechanisms evolved from some common ancestor. It's not reasonably to say that flight is a "convergent feature" of birds, bats and insects because the underlying mechanisms are not remotely similar. So there are NO features that birds, bats and insects share that are closer to each other than they are to other animals in their class. A bat's wing is much more similar to (say) a mouse's fore-feet than it is to a bird's wing. The flight muscles of an insect are not remotely related to the flight muscles that a bird use. This hypothesis is so far from being possible - it's utterly untenable. SteveBaker (talk) 22:39, 15 June 2010 (UTC)

This just keeps getting better -- Thanks Steve. DRosenbach ^{(Talk | Contribs)} 02:07, 16 June 2010 (UTC)

It doesn't address your question directly, but it's important to note that relationship markers are specifically chosen that would not generally be influenced by natural selection. Besides fenestrae, one of the favourite markers used are the foramina of the skull. While they're obviously required for blood vessels and/or nerves, their exact number and placement won't usually be exposed to evolutionary pressure. For example, if the supraorbital artery was to come of from the middle of the frontal bone instead of the supraorbital notch, it's not likely that it would exert much pressure in terms of differing levels of offspring survival. Our article doesn't mention it, but I believe the relationship between Nanotyrannus and T. rex, for example, was determined using one or more of the facial nerve foramina. The point being, of course, is that the last thing you want to use is something that will directly affect genetic survival; if you wanted to determine whether your boots and coat were made by the same manufacturer, you wouldn't try to examine the materials (those would be made to "suit the environment"), you'd check the label, which wouldn't be under that pressure. Matt Deres (talk) 16:40, 16 June 2010 (UTC)

question about the supernova

do stars makes a small explodes/core collapses before they explode as a supernovae or novae? do the information in this link means that? and if this is right, how much of time between every explode and the other? do this happen with a certain types of the supernovae? and do information in this section of the supernova article talking about the same thing? (quote: "This process repeats several times; each time the core collapses, and the collapse is halted by the ignition of a further process involving more massive nuclei and higher temperatures and pressures.") --Abbad Dira (talk) 12:34, 15 June 2010 (UTC).

For the first, it's important to note that novae and supernovae are two completely different processes that just happen to have unfortunately similar names (because, from Earth, they appear superficially similar). The APOD link refers to novae, and our article notes that "astronomers theorize... that most, if not all, novae are recurrent, albeit on time scales ranging from 1,000 to 100,000 years" (a citation is provided). So yes, they have an ongoing pattern of explosions, which probably vary in size to some extent or another.

For supernovae, what you've quoted refers to internal fusion processes, which are unrelated to externally falling matter as discussed at the nova reference. Those collapses are the result of the star exhausting its supply of fusible material at current core temperatures and pressures. When fusion ceases, the forces counterbalancing gravity cease and the core begins to collapse. That collapse leads to ever higher temperatures and pressures, until conditions are such that a heavier element becomes fusible and a new temporary balance is restored, up until a nickel-iron core forms, which leads to the supernova. The star almost certainly flares and whatnot in the buildup to the supernova, which might be characterized as explosions (see Eta Carinae for one current example), but there are no small-scale supernovae before the actual supernova. — Lomn 13:04, 15 June 2010 (UTC)

thank you very much. quote:

"The star almost certainly flares and whatnot in the buildup to the supernova, which might be characterized as explosions"

can this flares makes a notable changes in the star magnitude? and thank you again --Abbad Dira (talk) 07:35, 16 June 2010 (UTC).

Beer nutritious

Is it appropriate to call beer "nutritious" as we do in our Ale article? In what sense is "Small beer" "highly nutritious"? The Hero of This Nation (talk) 13:51, 15 June 2010 (UTC)

Lots of calories, if you consider that nutrition. --Chemicalinterest (talk) 14:36, 15 June 2010 (UTC)

If you consider Real ale, then the yeast will provide plenty of B vitamins. In years gone by, when water was in short supply if not downright poisonous, then beer would be a very useful source of nutrition, not to mention hydration. Small beer, being the drink of the poor, would have provided a large chunk of their daily nutritional requirements. Some countries classify beer as "liquid bread" (I believe that's the case in Belgium, where their licensing laws allow beer to be sold as a food), which makes sense because the ingredients are essentially the same. And of course, if you drink beers such as wheat beers, which are neither filtered nor allowed to drop clear, you're getting plenty of nutrients from the suspended sediment. --TammyMoet (talk) 14:42, 15 June 2010 (UTC)

Beer only provides some B vitamins. Chronic alcoholics go mental because their liquid diet lacks one of the B vitamins in particular, I forget which. Other consumables provide far better nutrition - for example an apple or apple juice. So beer cannot be said to be "nutritious" enough to warrant calling it so. 92.15.28.6 (talk) 23:13, 15 June 2010 (UTC)

You're thinking of pellagra, generally caused by a niacin (vitamin B₃) deficiency. Alcoholics with pellagra have typically gone so far as to have abandoned food all together. It makes sense that they would probably also prefer distilled liquors to the far more nutritious beer. – ClockworkSoul 02:44, 16 June 2010 (UTC)

It is also lacking B12 for example, and probably others. If you ranked all commonly available drinkable items according to how "nutritious" or healthy they are, then I expect beer would come towards the bottom of the list. Calling it "nutritious" is a weasel word that is meant to label it as healthy, when it is not. 92.28.251.43 (talk) 11:30, 16 June 2010 (UTC)

The context the word "nutritious" is used is small beer in medieval Europe. Small beer is thick and unfiltered. It would probably wind up near the top of your nutrition list of commonly available medieval beverages. APL (talk) 14:32, 16 June 2010 (UTC)

Especially if the rest of the list is whole milk, wine, and "the water everyone's been shitting in". :-) Matt Deres (talk) 16:44, 16 June 2010 (UTC)

I beieve milk and wine are better for you than beer. Implying that beer is germ-free is not the same as being nutritious. 92.15.14.87 (talk) 17:12, 18 June 2010 (UTC)

Quite! And also bear in mind that describing something as "nutritious" or even "highly nutritious" is very far from saying that it supplies all nutritional needs and that one could live on it with no other dietary input. Incidentally, "small beer" was so called because it had the lowest alcoholic content of the various 'grades' (usually three) available. 87.81.230.195 (talk) 17:36, 16 June 2010 (UTC)

If you put it that way, then name me any normally consumed food or drink that is not 'nutritious'? If everything is nutritious, including food in medieaval times, then should not each and every food be described as nutritious? (Water is nutritious - try not consuming any). 92.15.14.87 (talk) 17:10, 18 June 2010 (UTC)

You understand that "Small beer" has very little resemblance to the cool, refreshing beverage we now enjoy at the local pub? It was probably much too high calorie for those of us with non-physical jobs who don't get enough exercise, but I don't see why it wouldn't contain a reasonably good assortment of nutrients. Much more-so than any bottle of regular beer you might find in the supermarket.

Of course, Let's not forget that if you're a laborer in medieval times, your body needs lots of calories. Calories are a form of nutrition, and small beer would be an inexpensive way of getting them.

Perhaps you are confusing "nutritious" with "healthy"? APL (talk) 21:46, 18 June 2010 (UTC)

See the mention of weasel word above. Calling it nutritious is just an excuse for boozing, and implying its healthy covers up its bad effects. 92.15.4.168 (talk) 12:23, 19 June 2010 (UTC)

The article mentions that small beer has just enough alcohol to act as a preservative, and not enough to cause intoxication (and having drunk it throughout the day for several weeks, I can confirm this). That fact, along with the fact that small beer is unavailable as a commercial product nowadays, means calling it nutritious clearly isn't "an excuse for boozing". 81.131.37.105 (talk) 14:01, 19 June 2010 (UTC)

Immediately preceding the "highly nutritious" assertion is a sentence mentioning gruit, which shouldn't be overlooked and I think was intended to be connected. I have actually brewed and drunk small beer during a month-long 16th c. recreation; lots of herbs go into the tun (and the mash is nice to eat for breakfast). 81.131.52.194 (talk) 09:03, 19 June 2010 (UTC)

Beer is indeed more nutritious than water, and small beer is more nutritious than strong filtered beer. Though, of course, thinking of "nutritiousness" as a linear scale is a recipe for disaster, given that we need all kinds of nutrients, and not too much of any of them, and not too much alcohol either come to that. It might be better to say that beer was a valuable component of the medieval diet. 81.131.37.105 (talk) 14:01, 19 June 2010 (UTC)

Transplanted lungs

This link from Yahoo! news describes a 28 year old British cystic fibrosis patient who received a lung transplant from a deceased smoker. The British government official overseeing transplant stated that a transplant isn't a guarantee of a "brand new" organ but that smokers' lungs can function normally. If anyone out there is a doctor or nurse, researcher, student, etc. experienced with the respiratory system, how plausible are that official's comments? A "brand new" organ is not admittedly neither necessary or possible in the case of human transplants, but as a general remark, would medical science approve of transplanting a smoker's lungs? Or only if they were a really light smoker? Is a matter of degree (spectrum) or of kind?--达伟 (talk) 14:00, 15 June 2010 (UTC)

The problem as I understand is that so few lungs area available for transplant that such 'sub-optimal' organs are being used. The main issue appears to be that the recipient was not informed. Mikenorton (talk) 14:10, 15 June 2010 (UTC)

[4] from Australia mentions one of the criteria is "20 pack-years smoking". I don't know what that is but perhaps it means 1 pack a day for 20 years, or 2 packs a day for 10 year etc. It also mentions it was an uncommon reason (along with age) for rejecting lungs. There are other criteria including relating to lung function that some smokers may fail. :[5] from Australia mentions one of the criteria is "20 pack-years smoking". I don't know what that is but perhaps it means 1 pack a day for 20 years, or 2 packs a day for 10 year etc. It also mentions it was an uncommon reason (along with age) for rejecting lungs. There are other criteria including relating to lung function that some smokers may fail.

These [6] [7] [8] discuss some of the problems relating to sub-optimal organs. They also mention that the criteria are changing anyway. However I would note it's not clear whether the lungs in question were considered sub-optimal under the criteria. Presuming the donor was a light smoker say half a pack a day for 30 years then the donor may not have meet the 20 pack-years if I understood it correctly and the lung functions may have been considered sufficient. Of course those are from Australia anyway and over 10 years old.

From the refs, I gather one of the problems is that transplant authorities don't like recepients cherry-picking organs (and I can understand this). While they may support informed consent, the consent needs to be given before hand so you can't list the donor's lifestyle and potential risk factors afterhand and ask them only to find they reject the organ and then it potentially goes to waste if you can't find another recepient in time. And I would guess filling out a 50 question yes or no on all the potential risks for a profile beforehand on what they're willing to accept is way too complicated particularly given the fact you really want to patient to actually understand the risks and not just think 'well that sounds bad' so you'll need to explain to them (and even I think we've established before most people are bad at evaluating risks).

Ultimately as with many things medical, it's a delicate balancing act between too much information which will just confuse the patient and lead to what many would consider poor decision making and ensuring informed consent.

When it comes to a smokers lungs the cancer risk (similar to the e.g. HIV and Hepatitis C risks one of the refs mentioned) from a smokers lungs particularly given the immuno-suppresants that would have to be used is an obvious concern.

Nil Einne (talk) 15:24, 15 June 2010 (UTC) Nil Einne (talk) 15:24, 15 June 2010 (UTC)

On the other hand, you have to weigh up the benefits to the patient. If I had the choice of five miserable years of life with a terminal illness against ten better years of life then being killed by my transplanted organ, I know which option I'd choose! [the time-scales are only for illustration, BTW: we don't know the prognoses of this patient] Physchim62 (talk) 15:43, 15 June 2010 (UTC)

Well yes. Although I think that's obvious, otherwise the issue of sub-optimal organs wouldn't even come in to it. In this particular case, the patient doesn't seem to be happy with what happened so I presume that at least meant they weren't likely to die in a few weeks. And I presume it also meants they weren't expected to die within a few years even with a highly successful transplant with excellent lungs. But perhaps I'm presuming too much. In terms of choice it doesn't seem to have come in to it here which is the primary reason why it hit the news. But as illustrated in the refs and also in my summary paragraph (which I albeit added after your message although I didn't get an EC) this isn't that surprising and doesn't mean there was any wrongdoing. On a personal note from the very limited information available I do feel if I were in the women's circumstances I would be glad I got something but as I said there's very little information. In any case, the patient must believe they would have survived long enough to get a 'better' (by which I mean in their opinion) set of lungs. Nil Einne (talk) 15:52, 15 June 2010 (UTC)

This article gives a nice overview. In particular, "The major concern for using donors with a history of cigarette smoking is the potential for poor lung function due to the obstructive pulmonary disease and the risk of transplanting an undetected primary or metastatic cancer or for developing a malignancy in the donor lung in the years after the transplant.... There are, however, no studies that directly address how much cigarette smoke exposure a donor may have before the lungs are not safe to use for transplantation. A donor history of smoking should therefore not prevent the use of donor lungs for transplantation." Axl ¤ [Talk] 17:44, 15 June 2010 (UTC)

The official's comment: "lungs from a smoker can be working perfectly normally" certainly is plausible. The key word is "can". Axl ¤ [Talk] 17:46, 15 June 2010 (UTC)

The main thing from smoking actually is cardiovascular disease, because of what nicotine does to the endocrine system. A lot of heart attacks coincide with being a smoker... which is probably half the reason for being out of breath. John Riemann Soong (talk) 15:46, 16 June 2010 (UTC)

clump of matter

Why isn't the universe one big clump of matter surrounded by space? 71.100.13.202 (talk) 14:51, 15 June 2010 (UTC)

Because all the way back at the Big Bang, the inflationary epoch laid down the seeds of structure formation via fluctuations. We observe later evidence of this in the cosmic microwave background radiation, the anisotropies of which are explained by the Big Bang model. Or, in short, because explosions are messy, uneven things. That's a very rough approximation, but it's a fair one. Later on, dark energy and the acceleration of the expansion of the universe play a role, too. — Lomn 15:17, 15 June 2010 (UTC)

For the first real proof of this, see COBE mission. Regards, --—Cyclonenim | Chat  17:15, 15 June 2010 (UTC)

It is a very profound question, OP (you should be a scientist), and while the generally-accepted theory for the singular universe (which indeed was a big clump of matter/energy) is inflation, at this point it still like saying "it is because it is". It's a great answer for "how", but not "why". While I have no problem accepting some "philosophically tidy" explanations for the cause of the Big Bang (such as chaotic inflation), there are many layers of complexity lying beneath, and if the history of science teaches us anything, a revolution in thinking occurs when that complexity is realized to indicate something even more simple. So indeed, why isn't the universe one big clump of matter? SamuelRiv (talk) 18:50, 15 June 2010 (UTC)

I assume that by "...be a scientist..." you mean obtain a degree in science and pursue science as a career. While that is great for people who want to live in a groove it is not so good for people who want unfettered comprehension; i.e., people who can not see the forest for the trees. 71.100.13.202 (talk) 23:29, 15 June 2010 (UTC)

Anthropic principle. Why isn't always the right question.-RunningOnBrains^(talk) 20:36, 15 June 2010 (UTC)

Sorry OP71.100, I should have said "become a scientist". I assumed (perhaps unjustly) you were a wide-eyed high-school student. And as I am in physics, I am possibly the "grooviest" if I take your meaning correctly - but those are the types of questions and philosophical concerns we do have to ask ourselves, even when dealing with everyday matter.

For example, right now we are working on a stable state that appears for a large number of moving things, ie a crowd of people walking across a bridge. This new stable state was discovered mathematically two years ago, but we don't have any record of it existing because nobody thought to look for it. The question of the "forest" now is whether or not it appears everywhere simply because it should, according to our results - were we so satisfied with our understanding of stable systems ten years ago that we ignored this state, even if it appeared, as some external complexity? These questions are important. SamuelRiv (talk) 01:24, 16 June 2010 (UTC)

I'm not against having knowledge or facts but rather the assumption that a person can not obtain all of them without pursuing a degree unless of course higher education is assuring itself work by sitting on facts and knowledge. If you believe that the Sun is at the center of the solar system and the university you want to attend insists that you admit that the Earth is really at the center of the universe then knowledge and fact have nothing to do with a degree or being a scientist. Why do you think so many college kids drink alcohol and smoke pot? 71.100.13.202 (talk) 22:33, 16 June 2010 (UTC)

Definition of "Earth's surface" for purposes of defining meteorites

If a meteor falls in a big city, lands on the top of a skyscraper, and somehow survives in one piece, is it considered a meteorite? The intro to Meteorite says: "A meteorite is a natural object originating in outer space that survives impact with the Earth's surface". Do definitions generally require it to land on dirt or in water, or does anything attached to dirt or water qualify? Nyttend (talk) 15:18, 15 June 2010 (UTC)

Yes. If it landed on a skyscraper, and the skyscraper is on the surface of the Earth, then it landed on (planet) Earth. (The word Earth here does not mean soil.)--Shantavira|^{feed me} 15:58, 15 June 2010 (UTC)

I think it means it's no longer whizzing through the air. So if you caught it in mid air it counts too, as long as you slowed it down. Ariel. (talk) 19:08, 15 June 2010 (UTC)

The distinction is between objects that burn up in the atmosphere and objects that don't. Even if you float yourself in a big old blimp and manage to catch one with a kevlar oven mitt, it's still a meteorite because it didn't burn up.

You might want to coat your kevlar with asbestos, because that will be one hot rock! Googlemeister (talk) 20:00, 15 June 2010 (UTC)

Not necessarily. The linked article says in part:

"Meteorites are sometimes reported to be warm to the touch when they land, but they are never hot. Reports, however, vary greatly, with some meteorites being reported as "burning hot to the touch" upon landing,[11][12] and others forming a frost upon their surface."

Most of the light visible from a falling meteor actually come from shocked and heated air. Only the outermost layer of the meteoroid itself gets heated up much, and this is then cooled both by heat exchange with the bulk of its interior (which is at outer-space temperature) and with the airflow as it drops after having slowed to terminal velocity. 87.81.230.195 (talk) 21:19, 15 June 2010 (UTC)

Am I misunderstanding something or is the quote sentence completely illogical and should be fixed? It seems like it's saying that "Meteorites are never hot, but sometimes they are burning hot". APL (talk) 14:41, 16 June 2010 (UTC)

I understood it to imply that some reports of meteorites being burning hot immediately after landing have been made, but were erroneous and based on a false assumption. However, of the three references cited in connection with this passage one is ambiguous, since it reports a meteorite being found in a hole made by a simultaneous lighting strike, one reports a small meteorite being hot to the touch within a minute of landing, and one reports a large meteorite being frost-coated. It makes some sense that the temperature might be size related. I agree that the passage needs some correction. 87.81.230.195 (talk) 17:31, 16 June 2010 (UTC)

Memory

Resolved

I asked this question before but didn't really get the type of answer I was hoping for, probably because I wasn't specific in my wording, so here goes again. What are some scientifically proven ways (techniques, foods, chemicals, etc) that improve memory? 82.43.90.93 (talk) 15:21, 15 June 2010 (UTC)

At the risk of sounding extremely stupid, have you considered revision? This is the most widely used technique to improve your recollection of a certain topic by simply repeating your study of it. If you're referring to a direct, automatic increase in memory, then I recommend reading the article on nootropics, but it's not well sourced. Regards, --—Cyclonenim | Chat  17:12, 15 June 2010 (UTC)

Have you not actually read the replies to your question on the Miscellaneous desk? --TammyMoet (talk) 17:19, 15 June 2010 (UTC)

I have read them, and as I said in my question here they aren't what I wanted. I realize my question on the Miscellaneousdesk was vague, so I've reworded my question and asked again on the science desk, hoping for a response that deals with scientifically proven methods, perhaps even with references.... 82.43.90.93 (talk) 17:52, 15 June 2010 (UTC)

He forgot. Axl ¤ [Talk] 17:48, 15 June 2010 (UTC)

Cross your fingers and say a prayer, while rubbing your lucky rabbit's foot. PMID 20511389 Rockpocket 17:59, 15 June 2010 (UTC)

There are no known methods that make memory substantially better in a general way across all situations. Stimulants such as amphetamine and caffeine improve memory while they are active, but the effects don't outlast the drug. Gaining knowledge about a domain improves memory for things in that domain, for example expert chess players have good memory for chess positions. And there are tricks such as the Method of Loci that can help in memorizing lists of arbitrary items. But there is no known treatment that makes memory "stronger" in a general way. Looie496 (talk) 18:04, 15 June 2010 (UTC)

Thank you for the informative answer :) 82.43.90.93 (talk) 18:08, 15 June 2010 (UTC)

Maybe these things will help: environmental enrichment, social stimulation, lack of social isolation [9], [10], [11]. Physical exercise, curcumin, and loads of other stuff in the nootropics article. --Mark PEA (talk) 18:16, 15 June 2010 (UTC)

So you haven't actually taken any notice of what I said, which was a practical method to improve your memory - that of writing things down and saying them out loud? It's a teaching method I have both experienced as a learner and used as a teacher. It works, otherwise I wouldn't have given it you. --TammyMoet (talk) 20:19, 15 June 2010 (UTC)

That is rote learning. What if the OP is trying to improve their memory skills so that if they were to witness a crime, they would give a reliable account of the events (as it's well documented how poor eye witness testimony is). You can't witness a crime and then ask the criminal to wait there whilst you write down what they are wearing, and say it out loud etc. --Mark PEA (talk) 21:10, 15 June 2010 (UTC)

To be honest, I don't think anyone in that situation will remember accurately everything they saw. The BBC did some research, which they aired recently, on just how unreliable witness testimony is. When I've been in those situations, I've stopped as soon as I can and wrote down what I can remember of the key points. This is an explanation of why eyewitness testimony is unreliable. http://www.open2.net/eyewitness/johanna_motzkau_witness_memory.html And another one: http://www.bbcfocusmagazine.com/feature/psychology/far-i-can-remember --TammyMoet (talk) 17:32, 16 June 2010 (UTC)

matter versus spirit

Why is matter even necessary? why isn't everything just spirit? 71.100.13.202 (talk) 15:24, 15 June 2010 (UTC)

Who says it's "necessary"? But this is way off into philosophy, and not a referenceable science question. — Lomn 15:33, 15 June 2010 (UTC)

Because every physical building block in our frame of reference is made of matter. If you figure out how to exist without being tied to matter, then it could become a debatable point. Until then, as Lomn said, it's just a matter of philosophy and maybe spirituality.

Without matter, where does 'spirit' come from? Your personality is entirely based upon matter, whether or not we understand it. Without this matter (the brain), you don't have thought or spirit. Regards, --—Cyclonenim | Chat  17:13, 15 June 2010 (UTC)

"Spirit" can be known as matter that is not understood by man. --Chemicalinterest (talk) 17:23, 15 June 2010 (UTC)

I've never heard it used in that sense, just as something that refers to our thoughts and personalities in a non-physical sense. It seems fairly evident, to scientists at least, that any/all of our thoughts are mere atomic interactions that are not understood. Regards, --—Cyclonenim | Chat  17:47, 15 June 2010 (UTC)

Even if you start with an assumption that the world is pure spirit, you find that it is governed by a number of regularities. Traced to the most fundamental level, these regularities show up as the laws of physics, such as conservation of energy, conservation of momentum, the Heisenberg Uncertainty Principle, and the principle of relativity, among others. The concept of matter can be viewed as a surrogate for these consistent regularities in our experience. Looie496 (talk) 17:33, 15 June 2010 (UTC)

Or... we can take the converse of that above and assert instead that because at the fundamental level it seems everything is described beautifully by largely a priori mathematical constructs, then no matter how we slice it the world is Rational, comprehensible, and perhaps even simply spiritual (entirely of the mind)? And wouldn't you know it, we even have an article! Definitely worth reading about and thinking about (even though I personally agree with what Looie summarized above). SamuelRiv (talk) 18:57, 15 June 2010 (UTC)

Basically: I think, therefore I am. Regards, --—Cyclonenim | Chat  20:38, 15 June 2010 (UTC)

Regards what? 71.100.13.202 (talk) 23:15, 15 June 2010 (UTC)

"Regards" is a formal way of ending a statement or later. It's like "yours sincerely" but slightly less formal. Regards, --—Cyclonenim | Chat  11:07, 16 June 2010 (UTC)

Latter-day Saints ("LDS" or "Mormons") believe that Spirit is matter-- just that it's more highly refined and mostly imperceptible.... Kingsfold (talk) 19:40, 17 June 2010 (UTC)

"Microrefineries" in the Gulf states

What would make impossible the idea of setting up small-sized refineries in which boats take in loads of crude instead of fish and get it into some kind of commercially usable format (if making gasoline is, as I already suspect, out of the question) they could make money off of? 20.137.18.50 (talk) 16:00, 15 June 2010 (UTC)

It's certainly not impossible, but rather a question of whether it's economical (or legal). Without doing research, I'd guess mostly the former: economy of scale is important to the oil industry. — Lomn 16:10, 15 June 2010 (UTC)

Keep in mind that the quantity (and concentration) of oil that is ecologically harmful is much smaller than the quantity (and concentration) of oil that is economical/profitable to collect. Otherwise, BP would be out there scooping up "every last drop" of spilled oil and selling it. Nimur (talk) 04:49, 16 June 2010 (UTC)

Carbon-based life more plentiful if system richer in Carbon?

"HD 108874 b is a gas giant announced in 2003. The orbit lies in the star's habitable zone. It is expected that any moons orbiting this planet are enriched in carbon, and are thus quite different than the silicate-rich bodies in our Solar System."

• Is a planet or planet-moon in system richer in Carbon likely to have more plentiful Carbon-based life than the average rock?? 24.78.167.139 (talk) 17:39, 15 June 2010 (UTC)

Leaving aside the fact we have no evidence of life anywhere except Earth? It's fairly obvious that if you have more carbon, you have a greater chance of carbon-based life than places where there are less carbon. At least it is to me. Regards, --—Cyclonenim | Chat  17:50, 15 June 2010 (UTC)

Well, it's obvious that you need a certain amount of carbon to support carbon-based life, but once you have that amount of carbon it isn't obvious whether more carbon would make life more likely. There is a theory that, if the conditions are suitable, life is essentially certain to arise (the main evidence for that is that life arose on Earth almost as soon as conditions were vaguely suitable, although it remained single-celled for several billion years, if memory serves). If it is certain, then the probability can't increase. --Tango (talk) 18:03, 15 June 2010 (UTC)

Sounds like a ton of observer bias in that theory, and with a sample size of about 1. Googlemeister (talk) 18:15, 15 June 2010 (UTC)

Yep. It's the best we can do, though. --Tango (talk) 20:22, 15 June 2010 (UTC)

Yes to all of the above, but we can make some assertions based on absolute chemistry. One thing that seems essential to current life is the rich variety of stable polymer compounds formed by carbon-chain-type molecules, something which does not occur to such a degree with atoms that bond preferentially on less than 4 points (so no nitrogen- or oxygen-based life on Earth). The second thing worth noting is that carbon, nitrogen, and oxygen are the first heavy elements formed in bulk in stellar fusion, at least for small-medium stars - so we don't have lithium or boron in high quantities at all, even though boron at least might form an excellent basis for polymer chemistry (??? I'm not a chemist - help me out here ???).

The alternative often given in sci-fi is silicon-based life, mostly because silicon forms in high quantities (most abundant heavy element in the Earth's crust) and bonds almost identically to carbon (right below it on the periodic table, so kinda like a heavy carbon: C++ ). However, that heaviness might be precisely what makes it a less-suitable candidate for forming life, as with weight comes decreasing electronegativity, so decreasing bond strength. I think those (again, not a chemist) are the fundamental assertions that we can make absolutely without having an example of life outside Earth. SamuelRiv (talk) 19:07, 15 June 2010 (UTC)

The issue is that silicon doesn't form pi bonds very well... it's less electronegative than hydrogen, the most abundant element in the universe. Thus Si-H bonds are considerably more activated (electron density on the outside) than C-H bonds (electron density near the middle part of the molecule). An important part of biochemistry is the ability for carbon to be both electron-donating or electron-withdrawing at the right moments, leading to rich aldol chemistry .... we don't see this with silicon. John Riemann Soong (talk) 19:23, 15 June 2010 (UTC)

Boron has a valency of 3 so, for the reasons you give, it isn't a good basis for polymers. It tends to form crystals with itself, rather than chains. --Tango (talk) 20:31, 15 June 2010 (UTC)

I wuv you guys! SamuelRiv (talk) 01:27, 16 June 2010 (UTC)

I look at the origin of life as a chemical reaction (or series of chemical reactions). In this case, more carbon would only increase the likelihood of the given reaction if carbon is the limiting reagent. If not, then more won't help, and could even hurt, if it displaces other reagents which are needed. StuRat (talk) 05:05, 16 June 2010 (UTC)

The last comment reads (If I may paraphrase) that excess Carbon can stifle the evolution of life because a certain amount of other elements need to be free. Have I got that correct? Awesome point by the way. So I coin the phrase "Diamond Desert Planet." 24.78.167.139 (talk) 05:59, 16 June 2010 (UTC)

well, keep in mind that carbon only makes up maybe 15%-20% of an organism (for humans it's 18%). The primary component, of course, is water, and the nature of a cell is to enclose a balanced environment which maintains a liquid solution of chemicals properly balanced for organic chemical reactions. Excess carbon (like other excess chemicals) is simply expelled from the cell to maintain that balance, so an environment with a great surplus of carbon materials might in fact be poisonous unless that carbon is bound up in non-water-soluble materials. --Ludwigs2 06:24, 16 June 2010 (UTC)

And to take this a bit further, I would expect that having all of the necessary ingredients for life in the same ratio as they are found in life is most likely to produce life. Thus, around 15-20% carbon would be ideal. Additional carbon might help if it displaces other elements not needed for life, but would be detrimental if it displaces other elements which are needed and in short supply on that planet. StuRat (talk) 15:15, 16 June 2010 (UTC)

Hummingbird feeders

I found a couple of interesting discussions in the archives, but nothing with regards to what I'd like to ask: Do hummingbird feeders need those plastic yellow flower parts? I ask because I have a feeder and it's hanging outside, but the plastic yellow flowers went missing (who knows what drove someone into removing them in the first place) and I'm hoping the birds can still figure out where the energy source is. – Kerαunoςcopia^◁_galaxies 18:10, 15 June 2010 (UTC)

No, at least not after the humming birds know where the feeders are. You may not attract the birds as quickly without the fake flowers or red die, but once they know where to find the nectar they don't need the visual cues. --Ludwigs2 19:25, 15 June 2010 (UTC)

You're right, they found the feeder and they couldn't care less about the flowers. The red dye is marketing BS though. The feeder is bright red, and that's obviously all they needed; I refuse to poison wildlife with the same additives we put in our own food to make our cheese look like cheese and bread look like wheat bread. It's sick. But anyway, feeder working fine, I was just curious. – Kerαunoςcopia^◁_galaxies 22:01, 15 June 2010 (UTC)

Probably a safe idea not to use it - there are plenty of allergies and side-effects that have occurred in humans due to food dyes (consider yellow #13). Since it's even harder to monitor the eggs and, umm, hyperactivity of hummingbird chicks, I'd think the sugar-plus-distilled-(tap)-water combo is safest. Good for you, OP. SamuelRiv (talk) 01:33, 16 June 2010 (UTC)

A hyperactive hummingbird sounds like it might flap so fast it's wings would fly off. :-) StuRat (talk) 04:57, 16 June 2010 (UTC)

Thanks SamuelRiv. I'll also caution against using distilled water, which could cause electrolyte imbalances. source: [12]. – Kerαunoςcopia^◁_galaxies 06:22, 16 June 2010 (UTC)

I wonder, is that something specific to hummingbirds, or is that just a retelling of the oft-repeated legend that distilled water will cause electrolyte imbalances in humans.

Of course, humans don't drink five times their body weight in bottled water... APL (talk) 14:14, 16 June 2010 (UTC)

I take it you've never been to a 2hr Hour Fitness club... --Ludwigs2 19:58, 17 June 2010 (UTC)

why doesn't centrifugation do some major damage to live cells?

The protocol I'm using to culture live HeLa cells calls for separation of the cells to be cultured from the old culture media via centrifuge ... I think at around 5000 rpm for 8 minutes. I can understand using this technique when trying to extract DNA -- we don't care about cells down the line, but live cells that are still metabolising, probably even still replicating DNA or even dividing? And HeLa cells (being cancer cells) are even all the more susceptible to metabolic or DNA damage.

Also why the emphasis on separating the cells from almost all traces of the previous buffer? Is it to prevent bacterial contamination? I mean, the cells seemed to be doing fine in the previous buffer -- or is it to induce the 'fresh serum effect'? John Riemann Soong (talk) 20:41, 15 June 2010 (UTC)

I don't know the answer to the first part of your question but I suspect it has to do with the fact that water behaves as a more viscous fluid at small scales, so that the flow of solution around cells and organelles as they move will be laminar and probably slow, thereby minimising potentially damaging shear forces. However that is just a guess. Also the fact that the cells will be almost neutrally buoyant will mean that the compressive forces on the cells will be much lower than would be expected intuitively, potentially preventing "crushing injuries" (again just an educated guess). For the second part: are you trypsinizing your cells before transfer (to detach them from the old flask), if so the trypsin needs to be removed or you will probably select for trypsin resistant cells, making future passage difficult. If you are culturing your HeLa in suspension rather than as attached cells this protocol from sigma-aldrich [13] says that centrifugation is only necessary if the previous medium has become acidic (i.e. yellow for phenol red indicator medium). I guess that this is because you need to reduce the amount of old medium added to the the new culture in this case to ensure the new culture starts at the correct pH. Some old medium is still added back in this protocol to ensure the correct growth factors are present etc. (unlikely to be an issue for HeLa cells). So my thoughts would be: for attached culture centrifugation is necessary to remove trypsin, for suspension culture centrifugation is probably not necessary but does no harm. I would say that the chance of removing bacterial contatamination by centrifugation is tiny (you could never remove all of the contaminated supernatent) and the extra handling steps probably slightly increase the risk of contamination if anything. Equisetum (talk | email | contributions) 21:38, 15 June 2010 (UTC)

OK, so you're sticking them on 5000 rpm, and it takes them eight minutes to make their way down to the end of the centrifuge tube; you're worried about the shear force... what's the shear force you put them under during the half-a-second that you squirt them out the end of a pipette then? ;-) Physchim62 (talk) 23:14, 15 June 2010 (UTC)

I may not have been very clear (actually, on reading it back I wasn't very clear ;)) but that is exactly my point - they take eight minutes because (I think) of the viscosity of the water surrounding them as well as their buoyancy, therefore shear force is not a problem. As you quite rightly point out the forces on cells will likely be much greater when pipetting than when centrifuging. Equisetum (talk | email | contributions) 23:27, 15 June 2010 (UTC)

A bit of back-of-the-envelope tells me that for any reasonably-sized benchtop centrifuge, 5000rpm will be equivalent to an rcf of about 1000-4000g, depending on rotor diameter. (And we're probably closer to the low end of that.) That sounds like a lot, until you realize that buoyancy is going to nullify a lot of that difference. The specific gravity of nucleated mammalian cells is generally on the order of 1.03 to 1.04, while the specific gravity of cell culture medium is somewhere north of 1.01 (mostly water, but topped up with salts and glucose, plus some other goodies.) That means that your cell spinning at 1000g is actually only experiencing a net force equivalent to 20-30g in air. While 20g is a lot for a human being, on the scale of a cell it's pretty negligible.

That said, unless there's a special reason why you're trying to get squeeze out all the old medium and get a really tightly packed pellet, 1000+g for a full eight minutes seems a bit excessive. I mean, 30 seconds at 300-500g is sufficient to pull down HeLa cells in a 15mL tube (unless you're using an oddly-high-density medium); I did it yesterday. TenOfAllTrades(talk) 15:06, 16 June 2010 (UTC)

Just a follow up question from the first respondent: Why exactly is 20-30g negligible on the scale of a cell? I know that it is, and it makes intuitive sense but I can't remember the precise physical reason why and that bugs me. I know that the force would be smaller according to F=ma, so force scales with mass/volume, so I guess the answer lies with what strength/resistance to deformation scales with?? Equisetum (talk | email | contributions) 20:46, 16 June 2010 (UTC)

Isolating elemental silicon

How can I isolate elemental silicon from quartz (SiO₂) without any expensive equipment? --75.25.103.109 (talk) 21:55, 15 June 2010 (UTC)

Try an aluminothermic process; react finely powdered aluminum with finely powdered silicon dioxide and ignite with a magnesium strip. PS: I think there might be something about the high melting point of silicon dioxide that would stop the reaction. --Chemicalinterest (talk) 22:10, 15 June 2010 (UTC)

You mean a 'silicon thermite' reaction - see here http://amazingrust.com/experiments/how_to/thermite.html#SiO2 or thermite

With access to an open fire (either coal, or coke, or a blacksmiths forge) mix powdered carbon (coke will do) with sand in a ceramic pot, and heat to about 2000C .. see Silicon#Production 87.102.18.94 (talk) 22:19, 15 June 2010 (UTC)

Open fires are generally not hot enough. That is why an electric arc furnace is normally used. --Chemicalinterest (talk) 10:59, 16 June 2010 (UTC)

If you use the reaction for its heat, then it is a thermite; but if you use the reaction in the extraction of metals, it is an aluminothermic reaction. --Chemicalinterest (talk) 10:58, 16 June 2010 (UTC)

Yes, it's a bit like a thermite reaction, so only do it on a small scale! Magnesium powder works better than aluminium powder in my experience. No need to ignite, just heat strongly in a covered crucible. Physchim62 (talk) 23:01, 15 June 2010 (UTC)

But how do you plan to separate the silicon from the oxides formed? Graeme Bartlett (talk) 01:58, 16 June 2010 (UTC)

Which reaction? - the silicon would be expected to be produced molten and sink to the bottom... but Alumina can be dissolved in NaOH.Sf5xeplus (talk) 02:36, 16 June 2010 (UTC)

That's one reason why magnesium is better than aluminium. With an excess of magnesium powder, you can simply dissolve the magnesium oxide (and excess magnesium) in dilute hydrochloric acid to leave elemental silicon. Not very pure silicon, mind, but enough to say that you've done it. Physchim62 (talk) 02:03, 16 June 2010 (UTC)

You can dissolve Al₂O₃ and Al powder in HCl too, just as well as Mg. --Chemicalinterest (talk) 10:58, 16 June 2010 (UTC)

reducing agents milder than NaBH4

AFAIK NaBH4 is still a little overkill... and a little pricey for some reactions with strong redox potentials. Redox-wise, are there any milder reagents that will reduce:

• chloramines into amines
• Ag(III) to Ag(0)
• peroxyethers (ROOR') into alcohols (ROH + R'OH or maybe an ether + alcohol)

Is it possible to couple the oxidation of formaldehyde to formic acid to actually reduce another aldehyde to an alcohol? (actually I'll cover this below). John Riemann Soong (talk) 22:15, 15 June 2010 (UTC)

ok I'll bite a bit:

• NaBH₄ is nearly dirt cheap at £30 for 100g, and down to 1/3 of that at kg quanties, plus the low 'molecular' weight of ~37g/mol they're practically giving it away..

Anyway - something cheaper:

• Hydrogen reduction - H₂ is cheap, but the catalysts can be expensive. Not everyone wants to work with hydrogen gas.
• Electrochemical reduction = particularily electrode generated H_{surface atom} is a nice way if you can get it to work. very cheap and safe.
  • For Ag(III) direct electrochemical reduction.
• Other cheap methods - all I can think of is acid + Zn or Fe or Sn ... (also Fe(II) and Sn(II) reductions) - you might have to do original research to see if it works. There's too many possibilities here for me to search all of them.
• For the chloramine possibly Mg reduction.87.102.18.94 (talk) 22:39, 15 June 2010 (UTC)

A rusty iron nail will do all of those reductions at negligeable cost: I can't guarantee the isolated yield after work-up, mind... Physchim62 (talk) 22:55, 15 June 2010 (UTC)

Why do you need it rusty? --Chemicalinterest (talk) 11:02, 16 June 2010 (UTC)

Because you want to keep your clean nails for hammering into things! Seriously, the role of the rust is just to make sure the reaction mixture can find it's way to some iron underneath – a "clean" metal surface usually has a good tough layer of oxide on it (this is why aluminium foil doesn't spontaneously burst nto flames) and that can slow down the reaction to the point of uselessness. Physchim62 (talk) 11:26, 16 June 2010 (UTC)

A nail dipped in HCl should contain some reactive iron on the surface rather than a passivating layer. --Chemicalinterest (talk) 13:29, 16 June 2010 (UTC)

Would ascorbic acid be good for any of them? --Chemicalinterest (talk) 11:12, 16 June 2010 (UTC)

Ascorbic acid would certainly do the silver reduction, as would glucose for that matter. Physchim62 (talk) 11:26, 16 June 2010 (UTC)

How do I activate these carbohydrate reducing agents? Do they need a catalyst? John Riemann Soong (talk) 16:34, 16 June 2010 (UTC)

Ooops, I was actually thinking Au(III)... I only started with gold recently so it's really weird for me to be using Au so often... John Riemann Soong (talk) 16:33, 16 June 2010 (UTC)

Au+++ should be easily reduced by any reducing agent, such as glucose or iron(II). --Chemicalinterest (talk) 20:59, 16 June 2010 (UTC)

using one aldehyde to reduce another aldehyde (product: alcohol and carboxylic acid)

It seems to me that aldehydes could disproportionate.

Consider the following reaction:

2 H2(CO) + HOH ----> HCOOH + CH3OH

Using standard heats of formation I think the overall reaction is -160 kJ/mol

Using acetaldehyde to produce acetic acid and ethanol, the reaction is less exothermic: -90 kJ/mol but it still seems sufficient to get a nice controlled reaction with the right catalyst. What catalyst would allow this disproportionation to occur? I assume that the reaction might be even more reactive if the formaldehyde wasn't stabilised by water but maybe dissolved in the right solvent.

Finally, is there any way to aim not for disproportionation but to actually have aldehydes reduce other carbonyl compounds? I imagine this would be quite useful. Maybe the reaction already exists? John Riemann Soong (talk) 22:32, 15 June 2010 (UTC)

You mean like the Cannizzaro reaction - as the article says for aldehydes with beta-carbon H atoms the aldol reaction predominates.87.102.18.94 (talk) 22:42, 15 June 2010 (UTC)

See also Cannizzaro_reaction#Variations for the 'finally' part .. yes.87.102.18.94 (talk) 22:43, 15 June 2010 (UTC)

The crossed Cannizzaro reaction with formaldehyde as the reducing agent is relatively common. Formaldehyde is cheap, so you can afford to throw away the formic acid by-product in a small scale synthesis. The practical problem is getting the formic acid out of the product mix. However, disproportionation is not the only self reaction that aldehydes can undergo: see paraldehyde, for example! Physchim62 (talk) 22:51, 15 June 2010 (UTC)

Something I find interesting is why aldehydes are less stable on average than alcohols or carboxylic acid derivatives, i.e. both oxidising and reducing an aldehyde is thermodynamically favourable. Are esters and carboxylic acids less electrophilic than aldehydes/ketones? I remember from electron density diagrams, esters/acids are somewhat turquoise? If so, why do some aldehydes not form stable acetals? John Riemann Soong (talk) 16:29, 16 June 2010 (UTC)

You're right...the carbonyl of an ester (or acid) is stabilized by resonance, whereas an aldehyde/ketone is not. And an aldehyde is also fairly unhindered, and the H electronics may play a role as well. So a carbonyl is still a very stable thing, but some carbonyls are much "less stabilized" by whatever makes a carbonyl stable. So some carbonyls are highly reactive and tend to form acetals given the opportunity. Formaldehyde is a pretty common case...exists as the hydrate when mixed with water, easily forms polyacetal chains and rings by itself. DMacks (talk) 18:16, 16 June 2010 (UTC)

Unknown concentration of NaOH

50.0 mL of 1.5 mol/L HCl was mixed with 40 mL of NaOH of unknown concentration. The temperature increased by 8.4 K. a) Calculate the heat of neutralisation of the reaction. b) Calculate the concentration of the NaOH used.
H = mcΔT/n
So 50*4.184*8.4/n
n?
n??
--203.22.23.9 (talk) 23:44, 15 June 2010 (UTC)

The HCl and NaOH should react in a 1:1 mole ratio. So moles of HCl = moles of NaOH. You can find the moles of HCl from the info you wrote above. That also equals the moles of NaOH. You can use that number of moles, and the volume to calculate the concentration. --Jayron32 01:40, 16 June 2010 (UTC)

Question makes no sense as asked - the assumption that moles HCl=moles NaOH is the only way to get a definate answer - but makes no sense - how could they know how much HCl to add if NaOH conc. was unknown.. We will never know.87.102.18.94 (talk) 03:32, 16 June 2010 (UTC)

No, they are given a concentration and a volume of HCl initially, to which the NaOH is added. Calculating the moles (n) of HCl is trivially easy to do. The question is easily answerable, and is of a type which most students should be able to solve in any introductory chemistry class. --Jayron32 03:35, 16 June 2010 (UTC)

If it had said neutralised or titrated then it would make sense.87.102.92.166 (talk) 14:46, 16 June 2010 (UTC)

I think "m" should be 90, i.e. 40+50. The whole thing's heating up, not just the HCl. - Jarry1250 ^{[Humorous? Discuss.]} 14:06, 16 June 2010 (UTC)